Semiconductor chips include contact pads that are electrically connected to external circuitry in order to function as part of an electronic system. The external circuitry is typically a lead array such as lead frame or a support substrate such as a printed circuit board. Electrical connection between the chip and the external circuitry is often achieved by wire bonding, tape automated bonding (TAB) or flip-chip bonding. For instance, with flip-chip bonding, ball grid array (BGA) packages contain an array of solder balls to mount on corresponding terminals on a printed circuit board, and land grid array (LGA) packages contain an array of metal pads that receive corresponding solder traces mounted on corresponding terminals on a printed circuit board.
Semiconductor packages may include a single chip or multiple chips. For instance, a semiconductor package may include stacked chips to increase packaging density. The stacked chips are typically attached to one another by an adhesive, mounted on a substrate and wire bonded to the substrate. The stacked chips can be disposed within a metal cap mounted on the substrate to improve heat dissipation. The chip at the top of the stack may have good heat dissipation through the metal cap. However, the chip at the bottom of the stack may have poor heat dissipation since it is thermally isolated from the metal cap, leading to reliability problems.
Therefore, there is a need for a semiconductor package with multiple chips that is compact and has excellent thermal and electrical performance.